Recovery of chroman derivatives

ABSTRACT

A process for recovering a concentrate of chromans from a distillate containing chromans is provided comprising the steps of: (1) forming chroman phosphates in the distillate; (2) subjecting the distillate to shearing forces, in the presence of a gas of flotation to form a froth; and (3) recovering the froth containing the concentrate of chroman phosphates.

FIELD OF THE INVENTION

The invention relates to a method of recovering a concentrate ofchromans from a mixture containing chromans.

BACKGROUND TO THE INVENTION

The chromans are a commercially valuable group of chemicals that showbiological activity as vitamin E and antioxidant properties. In thisspecification and the claims, the term “chromans” includes chroman andderivatives of chroman such as the hydroxy chromans tocopherol andtocotrienol (commonly referred to as the “tocols”), the alpha, betagamma and delta forms corresponding to 3,2,1 and 0 methyl groups. Theyare often used as dietary supplements. Chromans are second tier freeradical scavengers in animals and humans which work with vitamin C andubiquinone to minimize oxygen damage to cells.

Chromans are present in many natural lipids. Chroman concentrates areprepared from the “distillate” created while deodorising the lipids.Lipids are deodorised using a distillation process designed to removevolatile products. The volatile products are principally free fattyacids, but also include aldehydes from oxidation and many othersubstances. The molten lipid is either purged with super heated steaminjection or spread on a large surface in a flowing steam flux. Thevolatiles (including the chromans) and the steam are then condensed andthe non-aqueous fraction recovered as the “distillate”.

Presently, the main source of vitamin E is RRR-α-tocopherol derived fromsoybean oil. The raw oil is stripped with steam to strip the lowermolecular weight free fatty acid (“FFA”) from the oil which has amolecular weight three times that of the FFA. The chromans have asimilar molecular weight to the FFA and therefore follow the FFA intothe distillate. The distillate is then redistilled to give a higherconcentration of chromans. Typically, the chromans must then bemethylated to give vitamin E.

There are two main problems with the known process. First, if there is alow concentration of chromans, the relative vapour pressure between thechromans and the FFA in the distillate is insufficient to enablesatisfactory concentration. Second, during the distillation a highconcentration of tocotrienols, phytol and farnesene form and thesecompounds have a low vitamin E activity. Further, the process based on aseries of distillations is inefficient and uses a lot of energy andcapital plant.

As a result, investigations were made into developing a process toconcentrate chromans which avoids the high temperature refining process.

There is a well known art for concentrating hydrophobic molecules fromhigh surface tension bulk liquids such as water by using frothflotation. However, this art is not applicable to “distillates” whichare mainly C₁₈-C₂₂ FFA, because detergents suitable for aqueous systemsdo not stabilise a froth of FFA. The chromans present in the distillatedo not significantly accumulate on the air/fatty acid interface as bothmolecules have similar surface properties in the FFA phase.

Therefore, further investigations were made into the possible use offroth concentration to achieve a chroman concentrate.

DESCRIPTION OF THE INVENTION

It was found that the chromans can be concentrated by froth flotation ifthe chromans were activated by phosphorylation. The phosphorylatedchromans are insoluble in the FFA and form a brittle froth that containsa higher concentration of chromans than the FFA phase.

Accordingly, a process of recovering a concentrate of chromans from adistillate containing chromans is provided comprising the steps of:

(1) forming chroman phosphates in the distillate;

(2) subjecting the distillate containing chroman phosphates to shearingforces, in the presence of a gas of flotation to form a froth; and

(3) recovering the froth containing the concentrate of chromanphosphates.

In one preferred form, the froth could be further stabilised byadditions of small quantities of silicone surfactant and water.Preferably, the silicone surfactant concentration is between 0.01 to0.0001%.

The froth could also be further stabilized by the addition of a sugarsuch as glucose. The sugar is added to complex with the chromanphosphates and would typically be present in a mole ratio to thechromans of 0:1 to 2:1. The froth can also be stabilized by forming achroman phosphate salt with sodium or potassium.

Any convenient method of phosphorylation can be used to form the chromanphosphates. Typically, the phosphorylation is performed by addition ofexcess of poly phosphoric acid (eg about 50% mole excess), with strongstirring to generate an emulsion in the molten fatty acid. Thephosphorylation reaction may be further enhanced by the addition of asoap such as sodium oleate (eg three moles of soap relative to the polyphosphoric acid), then by allowing the reaction to proceed for 15 to 45minutes (preferably about 30 minutes). The addition of a soap increasesthe solution concentration of the reagent.

Preferably, the chromans are phosphorylated using P₄O₁₀ as per themethod disclosed in Australian provisional patent application PQ0374(International Publication Number WO 00/69865) at a temperature at whichthe FFA is liquid. The contents of Australian provisional patentapplication PQ0374 (International Publication Number WO 00/69865) arehereby incorporated by reference. The P₄O₁₀ is used in equal mole ratioto chromans. Typically, the amount of chromans is 1% of distillate.

Preferably, the temperature at which the process is carried out variesfrom the melting point of the “distillate” to about 200° C.

The gas of flotation used in the process is preferably air, but othergases inert to the process may be used. For example carbon dioxide ornitrogen gas would be suitable as gases with limited solubility but yetcapable of generating bubbles where there is a finite surface tension atthe gas/liquid interface.

Preferably, the shearing forces are applied using an aerator. Theaerator must be capable of generating a stream of bubbles of no morethan 3 mm diameter. In this respect, the aerator will give shearsufficient to intimately mix the distillate with the chemical additives.Standard aerators used for froth flotation are not suitable for viscousmaterial.

EXAMPLES

The invention will now be further illustrated by the followingnon-limiting examples.

Example 1

A flotation vessel was formed as a cylinder of diameter 50 mm and height300 mm with a lipped port 40 mm from the top as the froth exit. Thevessel was filled to 30 mm below the port with molten distillate, then ahigh shear stirrer and gas line inserted to the bottom. 4 g ofpolyphosphoric acid were added slowly with stirring, then 8 g of sodiumoleate soap, whilst maintaining the temperature at about 70° C. After 30minutes stirring air was introduced near the stirrer to generate a finestream of bubbles. A froth formed which was stabilised to allow bubblesto pass over the lipped port by careful addition of silicone oil andthree drops of water. The froth was recovered and analysed to find 0.67%tocopherol whilst 0.16% tocopherol was found in the bulk phase.

Example 2

A flotation cell was configured as an octagonal vertical vessel with atapered bottom and glass lined.

The vessel was partially filled with palm oil fatty acid distillate (293kg) and brought to 75° C. by using hot water in the jacket of thevessel. Once the distillate was at 75° C., the volume was corrected tobe 50 mm below the top lip of the vessel.

A pump was used to pump the molten distillate through the aerator deviceand back into the vessel to discharge 250 mm below the liquid surface.

P₄O₁₀ (870 g) was added over 3 minutes using the agitation of thecirculating pump, and a conditioning period of 5 minutes was allowed forreaction. The air supply to the aerator was slowly increased and SilwetL-7622 (a silicone surfactant) (6 g) and water (230 g) added slowly togive a froth that was sufficiently stable to pass across the lip of thevessel into a launder.

The initial concentration of alpha tocotrienol was 0.71%. The froth wascollected to give 9.8 kg of concentrate that contained 5.1% of alphatocotrienol and 0.41% of alpha tocopherol.

The word ‘comprising’ and forms of the word ‘comprising’ as used in thisdescription does not limit the invention to exclude any variants oradditions.

Modifications and improvements to the invention will be readily apparentto those skilled in the art. Such modifications and improvements areintended to be within the scope of this invention.

The claims defining the invention are as follows:
 1. A process ofrecovering a concentrate of chromans from a distillate containingchromans comprising the steps of: (a) forming chroman phosphates in thedistillate; (b) subjecting the distillate containing chroman phosphatesto shearing forces, in the presence of a gas of flotation to form afroth; and (c) recovering the froth containing the concentrate ofchroman phosphates.
 2. A process according to claim 1 wherein the frothis stabilized by addition of silicone surfactant and water.
 3. A processaccording to claim 2 wherein the silicon surfactant concentration isbetween 0.01-0.0001%.
 4. A process according to claim 1 wherein thefroth is stabilised by addition of sugars.
 5. A process according toclaim 4 wherein the sugar is glucose.
 6. A process according to claim 5wherein the glucose to chroman mole ratio is up to 2:1.
 7. A processaccording to claim 1 wherein the chromans are phosphorylated usingpolyphosphoric acid.
 8. A process according to claim 1 wherein thechromans are phosphorylated using P₄O₁₀.
 9. A process according to claim1 wherein the temperature at which the process occurs is in the rangefrom the melting point of the distillate to 200° C.
 10. A processaccording to claim 9 wherein the process occurs at a temperature in therange from 70° C. to 100° C.
 11. A process according to claim 1 whereinthe gas of flotation is selected from air, carbon dioxide, nitrogen orother inert gases.
 12. A process according to claim 11 wherein the gasof flotation is air.
 13. A process according to claim 1 wherein theshearing forces are applied using an aerator.
 14. A process ofrecovering a concentrate of chromans from a distillate containingchromans comprising the steps of: (a) forming chroman phosphates in thedistillate; (b) subjecting the distillate containing chroman phosphatesto shearing forces, in the presence of a gas of flotation and astabilizer selected from the group consisting of silicone surfactants,sugars and mixtures thereof to form a froth; and (c) recovering thefroth containing the concentrate of chroman phosphates.
 15. A process ofrecovering a concentrate of chromans from a distillate containingchromans comprising the steps of: (a) forming sodium or potassiumchroman phosphate salts in the distillate; (b) subjecting the distillatecontaining chroman phosphates to shearing forces, in the presence of agas of flotation to form a froth; and (c) recovering the frothcontaining the concentrate of chroman phosphates.
 16. A process ofrecovering a concentrate of chromans from a distillate containingchromans comprising the steps of: (a) forming chroman phosphates in thedistillate using a phosphorylating agent selected from the groupconsisting of polyphosphoric acid and P₄O₁₀; (b) subjecting thedistillate containing chroman phosphates to shearing forces, in thepresence of a gas of flotation to form a froth; and (c) recovering thefroth containing the concentrate of chroman phosphates.
 17. A process ofrecovering a concentrate of chromans from a distillate containingchromans comprising the steps of: (a) forming chroman phosphates in thedistillate at a temperature in the range of from 70° to 100° C.; (b)subjecting the distillate containing chroman phosphates to shearingforces, in the presence of a gas of flotation to form a froth; and (c)recovering the froth containing the concentrate of chroman phosphates.18. A process of recovering a concentrate of tocopherols andtocotrienols from a distillate comprising the steps of: (a) formingtocopheryl phosphates and tocotrienol phosphates in the distillate; (b)subjecting the distillate containing tocopheryl phosphates andtocotrienol phosphates to shearing forces, in the presence of a gas offlotation to form a froth; and (c) recovering the froth containing theconcentrate of tocopheryl phosphates and tocotrienol phosphates.